Analysis of Trihalomethanes - University of Massachusetts Amherst

33 Pages·2012·0.19 MB·English

UMass Environmental Engineering Program

Analysis of Trihalomethanes
and Related Pentane-Extractable Organic Halides

File: THM SOP ver3.docx
As performed at the University of Massachusetts, Last Modified: 4/21/2012 1:59:00
Environmental Engineering Research Laboratory PM
Printed: 12/28/2012 5:19:00 PM

Prepared by:
David A. Reckhow 413-545-5392
18 Marston Hall [email protected]
University of Massachusetts
Amherst, MA 01003

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Table of Contents
Standard Operating Procedures ...................................................................................................................... 3
Scope .......................................................................................................................................................... 3
Method Overview ....................................................................................................................................... 6
Detailed Procedures .................................................................................................................................... 7
Basis for Method .................................................................................................................................... 7
UMass Detailed Procedures .................................................................................................................... 9
Sample Preservation ........................................................................................................................... 9
Sample Extraction and Preparation for GC Analysis ....................................................................... 10
Analysis by Gas Chromatography .................................................................................................... 11
Data Analysis & QC Reporting ........................................................................................................ 11
Clean Up ........................................................................................................................................... 13
Standard Solutions, Solvents and Supplies ....................................................................................... 14
Quality Assurance/Quality Control .......................................................................................................... 19
General Approach ................................................................................................................................. 19
Quality Assurance Objectives........................................................................................................... 20
General Procedures ........................................................................................................................... 20
Procedures specific to Chromatographic Analysis ........................................................................... 20
Data Quality Indicators ..................................................................................................................... 22
Sampling Custody ............................................................................................................................ 23
Sample Collection and Storage ......................................................................................................... 24
Handling and Storage of Standards and Reagents ............................................................................ 24
Data Reduction, Validation and Reporting ....................................................................................... 24
Procedures specific to THM Analysis .................................................................................................. 26
General Analytical QC ..................................................................................................................... 26
Special QC Tests .............................................................................................................................. 28
QC Criteria ....................................................................................................................................... 30
USEPA Method 551.1: (Revision 1.0) ................................................................................................... 33

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Standard Operating Procedures

Analysis of Trihalomethanes
and Related Pentane-Extractable Organic Halides

This guidance document was prepared to assist research assistants, post-docs and
lab technicians in conducting trihalomethane (THM) analysis in the UMass
Environmental Engineering research laboratories. It aspires to outline our standard
operating procedures, as they exist at the present time. It also emphasizes elements of
quality control that are necessary to assure high quality data. Thanks go to Allan Briggs,
Melissa Brown and Amanda Keyes for providing summaries of our revised practice since
moving into Elab II. Please help me keep this document current by alerting me to any
long-term changes in methodology or equipment.

Dave Reckhow
Faculty QC officer for THM analysis

Scope

This method has been used in the UMass Environmental Engineering Laboratory
for all 4 trihalomethanes and all 3 dihaloacetonitriles containing chlorine and bromine, as
well as several other chlorine-containing neutral compounds (analytes listed in Table 1).
It has been found to meet data quality criteria with all raw and treated drinking for which
it has been tested. This method should not be used for other media without further
validation.
Extension of this method some or all of the other halogenated analogues of these
compounds (Table 2) may be possible, however this has not been validated at UMass.
Any use of this method for compounds other than those in Table 1 must be accompanied
by appropriate disclaimers until the method can be fully validated. Chloral hydrate has
been found to be better recovered by ether extraction (e.g., MtBE), than by pentane. For
this reason, it is sometimes analyzed separately using an alternative LLE/GC/ECD
method, especially when low detection limits are desirable.

Table 1: Standard Neutral Extractable Analytes
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Analyte CAS Registry #
Trihalomethanes (THMs)
Chloroform 67-66-3
Bromodichloromethane 75-27-4
Chlorodibromomethane 124-48-1
Bromoform 75-25-2
Dihaloacetonitriles (DHANs)
Dichloroacetonitrile (DCAN) 3018-12-0
Bromochloroacetonitrile (BCAN) 83463-62-1
Dibromoacetonitrile (DBAN) 3252-43-5
Trihaloacetonitriles (THANs)
Trichloroacetonitrile (TCAN) 545-06-2
Haloketones (HK)
1,1,1-Trichloropropanone (TCP) 918-00-3
1,1-Dichloropropanone (DCP) 513-88-2
Chloropicrin (CP) 76-06-2
Chloral Hydrate (CH) 75-87-6

Table 2: Other Pentane Extractable Analytes
Analyte CAS Registry #
Iodinated-Trihalomethanes (ITHMs)
Dichloroiodomethane (DCIM)
Bromochloroiodomethane (BCIM)
Dibromoiodomethane (DBIM)
Chlorodiiodomethane (CDIM)
Bromodiiodomethane (BDIM)
Iodoform (TIM)
Iodinated-Dihaloacetonitriles (IDHAA)
Chloroiodoacetonitrile (CIAN)
Bromoiodoacetonitrile (BIAN)
Diiodoacetonitrile (DIAN)
Monohaloacetonitriles
Chloroacetonitrile
Bromoacetontrile
Brominated Trihaloacetonitriles
Bromodichloroacetonitrile
Dibromochloroacetonitrile
Tribromoacetonitrile
Halopropanones
1,3-Dichloropropanone
1,1-Dibromopropanone
1,1,3-Trichloropropanone
1-Bromo-1,1-dichloropropanone
1,1,1-Tribromopropanone
1,1,3-Tribromopropanone
1,1,1,3-Tetrachloropropanone
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1,1,3,3-Tetrachloropropanone
1,1,3,3-Tetrabromopropanone
Haloacetaldehydes
Dichloroacetaldehyde
Bromochloroacetaldehyde
Tribromoacetaldehyde
Halonitromethanes
Chloronitromethane
Bromonitromethane
Dichloronitromethane
Bromochloronitromethane
Dibromonitromethane
Bromodichloronitromethane
Dibromochloronitromethane
Bromopicrin

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Method Overview

Reproduced below is a simple, step-by-step outline of our THM method for quick
reference.

Table 3: Summary of Procedure for THM Sample Analysis
1. Prepare calibration standards (Table 4) and QC samples (Table 5)
2. Place 20 mL of sample/standard to be analyzed into vial.
3. If residual chlorine is present add approximately 40 mg of NH Cl
4
4. Add 4mL of the pre-mixed Pentane1 + internal standard.
5. Add approximately 15g of Na SO (Use dispenser made by glass shop.)
2 4
6. Shake for 15 minutes.
7. Transfer organic layer into autosampler vials
8. Freeze to remove water, and analyze.

Table 4. Typical Preparation of Calibration Standard
1. Prepare Stock II as needed: Add 100L of 551A commercial mix and 20L of the
551B commercial mix to a 10mL volumetric flask containing acetone.
2. Prepare calibration standards: add 20mL of Super-Q to 7 vials. Add 0, 5, 10, 20, 30,
50, and 80 L of stock II. Volumes of stock addition may be adjusted based on
expected HAA concentration range and speciation.

Table 5. Typical Preparation of QC Samples
1. Prepare Spiked samples for determination of matrix recovery (laboratory fortified
sample matrix). Select 10% of analytical samples and set aside an additional 20 mL
aliquot of each. Add either 20, 30 or 50 L of calibration stock II to each.
2. Prepare a continuing calibration check standard at the 50 g/L level.
3. Prepare any other QC samples as needed (see Table 10, page 26).

1 MtBE must be used in place of pentane if chloral hydrate is to be analyzed.
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Detailed Procedures

Basis for Method

We use a protocol that is closely aligned with the US EPA method 551.1,
“Determination of Chlorination Disinfection Byproducts, Chlorinated Solvents and
Halogenated Pesticides/Herbicides in Drinking Water by Liquid-Liquid Extraction and
Gas Chromatography with Electron Capture Detection.” Please refer to the latest version
of this method (currently version 1.0, dated 1990; attached as Appendix 1) for all details.
For historical reasons and site-specific considerations, we have chosen to depart
from method 551.1 in several minor ways. The most substantial differences include:
 Use of pentane; MtBE only used when chloral hydrate data are needed
 Smaller volumes of sample, reagents, and solvents
 Sodium arsenite sometimes used as a quench in place of ammonium chloride
 Addition of internal standard to solvent earlier in the procedure
 Volumetric rather than gravimetric determination of sample size

Once again, the primary source for our THM method is US EPA method 551.1.
This should be consulted whenever questions arise. However, the analyst should keep in
mind that we have made some specific modification. These are itemized below in Table
6.

Table 6. UMass Protocol Departures from US EPA Method 551.1
§ from Step or Material 551.1 protocol UMass protocol
551.1

1.7 Solvent MtBE Pentane (MtBE is only used when
chloral hydrate is to be quantified)
6.1 Sample Vials 60 mL size 40 mL size
7.1.7.1 Phosphate Buffer 99% KH PO and 1% 97.5% KH PO and 2.5% Na HPO
2 4 2 4 2 4
Na HPO
2 4
7.3.6 and Internal Standard Bromofluorobenzene is added 1,2-dibromopropane added to bulk
7.4.2 to pentane extracts solvent (300µg/L) prior to use for
extraction
11.1.2 Aqueous sample Removal of 10 mL from vial Addition of sample by pipet to vial
handling and gravimetric determination
of remaining volume
11.1.2 Sample volume 50 mL 20 mL
11.2.2.1 Pentane volume 5.0 mL 4.0 mL
11.2.2.2 Sodium Sulfate 20 g 15 g
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addition
11.2.2.3.1 Transfer to Quantitative (necessary due to Not quantitative
autosampler vial IS addition protocol)

We use one of our Hewlett-Packard 6890 GCs for THM analysis. These are
equipped with an HP 7673 autosampler. Our GC column and parameters are compared
to method 551.1’s column A (Table 1 in US EPA method) in Table 7 below.

Table 7. Instrument Parameters for THM Analysis
Step 551.1 protocol UMass protocol
Analytical Column DB-1 DB-5
Length 30 m 30 m
Internal Diameter 0.25 mm 0.25 mm
Film Thickness 1.0 µm 1.0 µm
Injection volume 2 µL 2 µL
Injection Type Splitless
Split Flow none
Carrier Gas Helium Zero-grade Nitrogen
Carrier Flow Sufficient for 25 cm/sec linear 1.5 mL/min
velocity2
Make-up Flow 30 mL/min
Injector Temp 200°C 175°C3
Detector Temp 290°C 275°C
Oven Program Hold at 35°C for 22 min Hold at 27°C for 10 min
Ramp to 145°C at 10°C/min Ramp to 41°C at 3°C/min (4.67
(11 min) min)
Hold at 145°C for 2 min Hold at 41°C for 6 min
Ramp to 225°C at 20°C/min Ramp to 81°C at 5°C/min (8 min)
(4 min) No hold
Hold at 225°C for 15 min Ramp to 180°C at 25°C/min (3.96
Ramp to 260°C at 10°C/min min)
(3.5 min) Hold at 180°C for 6 min
Hold at 260°C for 30 min

2 Evaluated at 35ºC
3 May need to be lowered for analysis of some labile non-THMs (see Krasner et al., 2001)
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UMass Detailed Procedures

Sample Preservation
1. Add one of the following quenches to each 40mL amber vial4.
 A. Add about 40 mg ammonium chloride (NH Cl) crystals (Desiccator in 301
4
Elab II) using dispenser made by glass shop (in drying cabinet above the
desk)5
 Converts free chlorine (FRC) to chloramines (CRC). Therefore, not
recommended for DBPs that will form directly from reaction with
chloramines (e.g., some dihalo compounds such as 1,1-DCP)
 Can cause low recoveries for chloral hydrate6 (EPA 551.1) and accelerate
degradation of iodinated THMs (Gonzalez et al., 2000)
 B. Alternatively, add 250 L of sodium arsenite solution7
 Not well studied, arsenite is toxic and must be handled with care
 May not rapidly reduce combined chlorine
 C. Alternatively, add an excess of ascorbic acid (e.g., 30 mg/L)8
 Ascorbic acid can accelerate decomposition of brominated
trihaloacetonitriles and brominated trihalonitromethanes (Krasner et al.,
2001)

2. Add buffer salts.
 Using the marked spatula, add one measure of the phosphate buffer (~1g)
 This is used to adjust pH to 4.5-5.5, and it is prepared according to the
section on: Preparation of Buffer Salt Mix (page 16)
 A lower pH buffer (pH~ 3.5) should be used if iodinated THMs and certain
HPs and HANs are to be measured (see: Gonzalez et al., 2000)

3. Be sure that the vial is filled headspace-free.
 Fill to just overflowing and cap with Teflon-lined septum (be sure that septum
doesn’t have any holes and that the teflon side is down)
 THMs are quite volatile and easily lost to the air
 This may not be necessary if sample is to be immediately extracted

4. Place vials with aqueous samples in a refrigerator until extraction.
 Samples should be extracted and analyzed as soon after quenching as possible,
but under no circumstances should more than 14 days be allowed to elapse.

4 clean, PTFE-faced septum capped vials; Hydrogen peroxide (1M/M, forming O and HO) is also effective at reducing chlorine
2 2
[Worley et al., 2003; JAWWA 95:3:109], but has not been adequately tested for THM analysis.
5 UNC adds 20 mg of ammonium sulfate to each 40-mL vial; this is dropped to 4 mg for HAN & HK analysis
6 sulfite can be used for analysis of chloral hydrate, but this is not recommended for most other DBPs.
7 0.1 N, kept in refrigerator # 3
8 Ascorbic acid reacts at 1M/M stoichiometry forming dehydro-accorbate [Worley et al., 2003; JAWWA 95:3:109].
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Sample Extraction and Preparation for GC Analysis9
1. Bring analytical samples to room temperature, and prepare calibration
standards and QC samples

2. Place 20 mL of sample/standard to be analyzed into vial.
 Add 20 ml of the water sample using an Eppendorf pipette10 (room 301)
 It is critical that samples be treated to avoid volatilization of analytes
 In our laboratory this is done by careful attention to quiescent sample transfer
and rapid addition of pentane as soon as the sample is exposed to air,
addition of sulfate and capping.

3. Add 4mL of the pre-mixed Pentane11 + internal standard.
 Use repeater pipet

4. Add approximately 15g of Sodium Sulfate (Na SO )
2 4
 One measure from the glass dispenser labeled THM.
 Dispenser is located in room 301 cabinet next to hood

5. Shake for 15 minutes.
 Cap vial
 Place vials in rack
 Secure rack with top into harness on New Brunswick G10 Gyrorotary shaker
 Turn on and set speed to 250 rpm
 Shake for 15 minutes.

6. Transfer organic layer (top) to autosampler vials.
 Use pasteur pipets
 Use vials as supplied without further cleaning
 Fill using a Pasteur pipet and small rubber bulb
 Must be done in hood
 Place clean top on vial and use crimper to seal
 Vials are marked with ID
 When all are complete, approximate liquid level in each vial should be
marked with a line using a permanent marker12.
 Be certain to include necessary QC samples
 See Table 10 (page 26) for a full listing of QC samples
 See Table 11 (page 27) for a typical sequence

7. Freeze Samples to remove water13
 Store autosampler vials in freezer for at least 3 hours

9 Typical prep time is 4 hours for a run of 30 samples
10 Samples are generally handled with a pipet designed for volatile liquids. We use an Eppendorf Maxipettor Model 4720 with “S”
tips (Brinkmann Instruments Inc., Westbury, NY.
11 Or MtBE if chloral hydrate is to be analyzed.
12 This is to help identify when excessive evaporation has occurred
13 since water is insoluble in pentane, any water is present as a separate phase
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